[imp] Problem with failed login

[Lino]

Hi!
I've got this message/error when i try to log with a wrong login/password:

An error has occurred. Furthermore, Horde encountered an error 
attempting to log this error. Please check your Horde logging 
configuration in horde/config/horde.php.

[linea 192 di /home/lino/htdocs/horde/lib/Horde.php]
*Notice*: (null)(): Login failed. (errflg=1) in *Unknown* on line *0*

*Notice*: (null)(): Login failed. (errflg=1) in *Unknown* on line *0*

*Notice*: (null)(): Login failed. (errflg=1) in *Unknown* on line *0*

*Notice*: (null)(): Too many login failures (errflg=2) in *Unknown* on 
line *0

*While with a right login/password all's well.

Can you help me to solve it please?

I've installed Horde/IMP latest version and i set IMP to handle the 
autentication for Horde.

Thank u very much.

Lino :)